1. Technical Field
The present invention relates to a semiconductor device, a manufacturing method of the semiconductor device, and the like.
2. Related Art
A semiconductor device that includes a lateral PNP bipolar transistor is used as a circuit element, for example. The transistor includes an N-type buried diffusion layer arranged in a P-type semiconductor substrate, a P-type epitaxial layer (semiconductor layer) arranged on the semiconductor substrate, an N-type impurity diffusion region (N-plug) that extends from a surface of the semiconductor layer to the buried diffusion layer to have a contact with the buried diffusion layer, and a deep N-well that reaches the buried diffusion layer.
In a manufacturing process of such a semiconductor device, forming the N-type buried diffusion layer under the P-type semiconductor layer, forming the N-plug that extends from the surface of the semiconductor layer to the buried diffusion layer, and forming a deep N-well that reaches the buried diffusion layer, which are not used in forming a MOS field effect transistor, are needed.
Also, there are cases in which a zener diode is formed as a circuit element in a semiconductor device. The zener diode is constituted by a PN junction of a high concentration P-type impurity diffusion region and an N-type impurity diffusion region. In general, the PN junction is formed by joining a P-type impurity diffusion region that constitutes a source or a drain of a MOS field effect transistor and an N-type impurity diffusion region. Note that forming the PN junction by adding another impurity diffusion region having a different concentration and adjusting the concentration thereof is needed when the specifications of the breakdown voltage are different.
Furthermore, there are cases in which an LD (Lateral Double-diffused) MOS field effect transistor is formed as a circuit element in a semiconductor device. In this case, forming an N-type buried diffusion layer under a P-type semiconductor layer, forming a deep N-well that reaches the buried diffusion layer, and forming a body region in a portion of the deep N-well, which are not used in forming a MOS field effect transistor, are needed.
A semiconductor device including a diode in which breakdown voltage fluctuation is suppressed is disclosed in FIGS. 1 and 2 of JP-A-2015-90913 (paragraphs 0008-0009, FIGS. 1 and 2), as a related technology. The semiconductor device includes a P-type epitaxial growth layer 13 provided above a silicon substrate 11 via an N-type buried layer 12, an element isolation region 17, 18 formed in the epitaxial growth layer 13, an N−-type cathode 14 that is formed in the epitaxial growth layer 13 and located inside the element isolation region 17, 18, and a P−-type anode 20 that is formed above the cathode 14 so as to be in contact therewith and covers an inner corner portion of the element isolation region 17, 18.
Incidentally, it is required that, in addition to the aforementioned lateral bipolar transistor, other types of circuit elements or a zener diode having a desired breakdown voltage are mounted together in the semiconductor device, in order to realize various circuits. Meanwhile, when an attempt is made to mount a plurality of different types of circuit elements together in the semiconductor device, processes for forming dedicated impurity diffusion regions for respective circuit elements increase, and the manufacturing cost of the semiconductor device increases due to the increased number of masks and processes.